Microphone



June} 24, 1930. R. A. KIEFER 1,767,242

MICROPHONE Filed March 11, 1929 ATTORNEY I Patented June 24, 1930 urrsn sarsarsstea MICROPHONE Application filed March 11, 1929. Serial No. 346,204.

The object of this invention is to provide mechanical means for detecting faint sounds and thereby locating or determining the cause of trouble under a great variety of conditions as in connection with the operation of machines and mechanical devices of every description, including fluid distributing systems and the like.

A further object is to provide means making it possible to carry on conversation with persons accidentally imprisoned in buildings, vaults, or ships, or to merely hear conversation in ordinary tones thru walls, closed windows, and other portions of buildings and the like, when it is necessary to use a device or devices of this kind in connection with detective work.

A further object is to provide a device for use in detecting defects in electrical, and

wave controlled devices.

A further object is to provide, in a mechanical device of this character, particular means for picking up faint sound vibrations and transmitting them to a diaphragm in sufficient volume to render them audible to the user of the device.

With the foregoing and other objects in view, the invention consists in the novel con struction and arrangement of elements de 3 scribed, illustrated and claimed, it being understood that modifications may be made within the scope of the claims without departing from the spirit of the invention.

In the drawings forming part of this application:

Figure l is a perspective view of the device.

Figure 2 is a view in vertical or longitudinal section.

Figure 3 is a view in elevation showing a modified construction in which a ball and socket joint or similar joint may be used in the detecting rod.

Figures 4 and 5 show sections, respectively thru a solid detecting rod and a tubular detecting element, either one of which may be used as the lower element of Figures 1, 2

and 3.

Figure 6 is a perspective view, showing another form of the device.

The device includes a metallic element, preferably formed of brass, and designated 10, this device providing a sound chamber and having an upper outwardly extending flange 11, threaded as shown in Figure 2, '55 for engagement bya hard rubber cap 12.

The cup-shaped element 10 has a downwardly extending neck portion 13 externally threaded for engagement by a tubular handle 1 1 or" suitable material. This element 14 is threaded internally at 15, and the threaded portion just referred to is engaged by threaded portion 16 formed on or carried by the detecting rod or similar device 17. This rod may also carry a collar, or flanged portion, as the case may be, designated 18, and ifmade separately, a rivet 19 will be employed. A flange or collar 20 engages the lower end of tubular element 14, and is carried by rod 17 The element 17 is preferably tapered as shown in the drawings, the lower pointed end being designated 21 and being adapted to contact with an element under vibration, even though very slight vibration,ex-

tremely faint sound vibrations being sub ject to detection by this instrument.

7 An essential feature of the device is the structure illustrated in Figure 2 within the sound chamber. A diaphragm 25 of mica or other suitable substance as for instance ferrotype tin, is mounted on the upper portion of the flange 11, and is retained by cap 12. Between this diaphragm, and connected therewith,and a concave end .portion of rod 1Z,a brass ball 28 and a coiled spring 29 are employed. These may be assembled in the most effective manner, depending upon' the material of the diaphragm, in part, and upon conditions to be met. 7 TnFigure'2 I have shown coiled spring 29 connected with a plate 30 adjacent to diaphragm 25 and contacting therewith. If the diaphragm is of mica a screw 81 will pass thru the diaphragm and will engage plate 30. The coiled spring 29 is preferably of German silver wire, but may be of other, suitable material, and plate 30 is in the present case, as illustrated in Figure 2,

soldered to the coil, and the latter is soldered to brass ball 28, the ball resting freely within concave socket 528.

By these means an extremely sensitive assembly is provided, responsive to sound vibrations of the kind previously indicated, and resulting from defects in the operation of machinery, mechanical and electrical appliances of various kinds, etc. Moreover the device has been found to be highly responsive in registering speech and musical sounds. V

Figure 3 shows a slight modification in which the rod 17 carries socket member receiving ball 36 carried by element 37 serving the same purpose as the lower portion of element 17 of the first form, but when the device is to be applied to an element of a machine, it is sometimes convenient to have the upper and lower portions of the instrument at an angle with each other, in order to easily make use of the device in the manner intended.

Figure t constitutes a section transversely of the element 17, or other similar element, and a modification thereof is shown in Figure 5 in which a tubular device 17 is employed, serving a similar purpose, but in same instances producing better results.

In Figure 6 a rod 17, assumed to corre spond with rod 17 of the main fo m, is shown as having mounted thereon (by means of set screw 40 passing thru a sleeve or the like 4:1), a paper cone 42, or other suitable device for receiving sound vibrations, whereby the microphone element shown conventionally at A will respond when vibrations altho faint are conveyed thru the air.

Having described claim 1. In a microphone, a diaphragm, a housing for the diaphragm, a rod and means for mounting the rod with one end portion the invention, I

' spaced from the diaphragm, a coiled metallic element and an externally curved element connected with each other, these elements being interposed between the rod and the diaphragm and bearing thereon, for the transmission of sound vibrations from the rod to the diaphragm.

2. In a microphone, a diaphragm, a housing for mounting the diaphragm and providing a chamber on one side thereof, a rod extending into the chamber, and a coiled metallic element and retaining means therefor interposed between the diaphragm and rod and bearing thereon.

3. In a microphone, a diaphragm, a housing for mounting the diaphragm and providing a chamber on one side thereof, a rod extending into the chamber, and a coiled metallic element and universally movable element interposed between the diaphragm and rod and bearing thereon.

RAYMOND A. KIEFER. 

